1. Field of the Invention
The present invention relates to an effect addition apparatus for adding a sound effect to an input signal.
2. Description of the Related Art
Various effect addition apparatuses for electronically adding effects such as chorus, echo, reverberation effects, and the like to a musical tone signal have been developed along with development of high-performance sound equipment. Some effect addition apparatuses employ an analog delay element such as a BBD. However, in an apparatus of this type, it is difficult to change effect characteristics, and an S/N ratio is considerably degraded. As a result, a natural effect tone cannot be obtained. In recent years, effect tones can be generated by real-time processing since digital signal processing techniques are improved, and high-speed, high-density logic elements are developed.
As an effect addition apparatus of this type, U.S. Pat. No. 4,472,993 (Futamese et al.) discloses a technique wherein a plurality of effect addition operations are time-divisionally performed by digital arithmetic processing, and the digital arithmetic processing contents in this case are desirably determined based on parameters and control data corresponding to the effects.
However, the conventional effect addition apparatus includes special-purpose circuits for an effect addition ciruit, and a tone color parameter changing means used for the effect addition operations, resulting in a complicated arrangement. When the tone color parameter is changed, the next waveform data depends on the previous waveform data. For this reason, a discontinuous point may be produced in waveform data to be stored or waveform data may be discontinuously read out, thus generating noise.
U.S. Pat. No. 4,570,523 (Futamese et al.) discloses a technique wherein a digital memory is used as a delay element, amplitude data obtained by sampling an input musical tone at a predetermined cycle are sequentially stored in the digital memory, and the amplitude data corresponding to a desired delay time is read out and is converted to an analog signal, thus generating a reverberation tone.
However, the technique in U.S. Pat. No. 4,570,523 has no disclosure about changing of a tone color parameter, and the problem of noise is left unsolved.